Question

I have a large python dict created from json data and am creating a smaller dict from the large one. Some elements of the large dictionary have a key called ‘details’ and some elements don’t. What I want to do is check if the key exists in each entry in the large dictionary and if not, append the key ‘details’ with the value ‘No details available’ to the new dictionary. I am putting some sample code below just as a demonstration. The LargeDict is much larger with many keys in my code, but I’m keeping it simple for clarity.

LargeDict = {'results':
[{'name':'john','age':'23','datestart':'12/07/08','department':'Finance','details':'Good Employee'},
 {'name':'barry','age':'26','datestart':'25/08/10','department':'HR','details':'Also does payroll'},
 {'name':'sarah','age':'32','datestart':'13/05/05','department':'Sales','details':'Due for promotion'},
 {'name':'lisa','age':'21','datestart':'02/05/12','department':'Finance'}]}

This is how I am getting the data for the SmallDict:

SmallDict = {d['name']:{'department':d['department'],'details':d['details']} for d in LargeDict['results']}

I get a key error however when one of the large dict entries has no details. Am I right in saying I need to use the DefaultDict module or is there an easier way?

Answer 1

Use the get(key, defaultVar) method to supply a default value when the 'details' key is missing:

SmallDict = {d['name']:{'department':d['department'],'details':d.get('details','No details available')} for d in LargeDict['results']}